The invention disclosed herein relates generally to energy management apparatus and methods, and more particularly to a system for controlling equipment operation according to a duty cycle which varies continuously with variations in a sensed condition, such as temperature, within a range of sensed condition values.
Heating and air conditioning equipment for large buildings consume substantial amounts of electrical energy. Over the years various duty cycling systems have been developed wherein, in each case, equipment is periodically turned on and off in accordance with some plan which is directed to more efficient operation with as little effect on the occupants and contents of the building as possible. The purpose of duty cycle control is thus to reduce operation time of controlled equipment without loss of desired control. Reduced operation time is possible with duty cycle control without accompanying disadvantages because the controlled equipment is used at a higher efficiency.
For temperature control systems, heating and cooling equipment operation time is a function of temperature. Duty cycling based on temperature compensates for reduced load under moderate temperatures and heavy loads under extreme temperatures. Some duty cycling systems involve periods or cycles having fixed lengths of time, such as five or ten minutes, for example, with the off times being represented as lesser lengths of time or percentages of the periods or cycles. These are referred to as duty cycling schemes which involve fixed period duty cycles with varying off times.